The present invention generally relates to methods and systems for converting heat energy to other forms of energy. In particular, the invention relates to devices for dissipating heat generated by electrical components.
Electrical components, such as integrated circuits, including a central processor unit (CPU) for a computer, and operating in close proximity in an enclosed electronic apparatus, produce heat. To prevent thermal failure of one of the electrical components in the enclosed electronic apparatus this heat needs to be dissipated. Enclosed electronic apparatuses are common and typically include personal computers, display monitors, computer peripherals, television sets, handheld personal digital assistants (PDAs), cellular phones, facsimile machines, video cassette recorders (VCRs), digital versatile disc (DVD) players, and audio systems.
Thermal management of the electronic components in the enclosed electronic apparatus is used to prevent an enclosed electronic apparatus from failing or to extend the useful life of the enclosed electronic apparatus. For instance, a typical CPU operating in a personal computer may operate at a temperature of 70xc2x0 C. without experiencing a thermal failure. Heat generated by a typical CPU, however, often reaches a temperature of 100xc2x0 C. Conventional methods for thermal management of the enclosed electronic apparatus provide that a high heat producing electronic component be attached to a heat sink and positioned within the enclosure of the electronic apparatus so that either air convection or forced air dissipates the heat from the enclosed electronic apparatus. These conventional methods expel the heat as waste energy.
Systems have been developed to recover electrical energy from waste heat in solar-concentrator heated fluids, and geothermal sources. These systems, however, require that the waste heat be between 100xc2x0 C. to 200xc2x0 C. for a practical thermoelectric conversion efficiency (i.e., recover and convert enough heat energy to compensate for system power consumption). Prior efforts to produce economical electrical power from lower temperature sources (primarily heat sources at less that 100xc2x0 C. or 70xc2x0 C. to 100xc2x0 C. ) have generally proven unsuccessful.
The present invention provides an apparatus and method for dissipating heat from a relatively low temperature heat source, such as an electrical component, and converting the dissipated heat to work energy, such as electricity.
In an embodiment, an apparatus includes a closed system chamber that has a first location adapted to receive heat from the heat source, and a second location adapted to dissipate heat away from the heat source. The apparatus may include a means to draw heat from the chamber, such as a heat exchanger that is thermally connected to the second location of the chamber. The apparatus also includes a fluid, such as a gas or liquid, that substantially fills the chamber. In addition, the apparatus includes a first energy converter located within the chamber that is in thermal communication with the first and second locations of the chamber via the fluid. The first energy converter may produce an acoustic wave, preferably a standing acoustic wave, in the chamber to transport heat from the first location to the second location and out to the ambient. In addition, the first energy converter may receive heat and convert at least a portion of the heat to electrical energy.
In an embodiment, the first energy converter preferably includes a first vibration member and a transducer that is operably coupled to the first vibration member. The first vibration member is adapted to vibrate in response to an electrical potential applied to the first vibration member and in response to a pressure change in the fluid. The first vibration member is also preferably adapted to vibrate at a predetermined resonant frequency of the chamber so that an acoustic or sound wave may be produced in the chamber to transport heat from the first location to the second location. The first vibration member is preferably disposed in proximity to an end of the chamber to prevent the formation of harmonics that may attenuate the acoustic wave. The transducer may be any electrical generator, such as a piezoelectric film, that is adapted to generate electricity from the vibration of the first vibration member.
The apparatus may include an electrical storage that is electrically connected to the transducer to capture and store the generated electricity. The apparatus may also include a power supply electrically connected to the first vibration member to selectively prompt the first vibration member to vibrate.
In an embodiment, an apparatus such as previously described further includes a second energy converter that has a second vibration member. The second energy converter may have a and a second transducer operably coupled to the second vibration member. Both the first and second vibration members are each adapted to vibrate in response to a pressure change in a fluid within the chamber and to a potential applied to the respective vibration member. In addition, the first and second vibration members are each adapted to vibrate at the predetermined resonant frequency of the chamber. The first vibration member and the second vibration member are preferably disposed equidistant from opposing ends of the chamber to produce a standing acoustic wave that extends the resonant length of the chamber that effectively transports heat from the first location to the second location of the chamber and out to the ambient.
In an embodiment of the present invention, a method for producing electrical energy is disclosed. The method generates a standing acoustical wave in a chamber having a predetermined resonant frequency in response to the vibration of a first and a second vibration member disposed equidistant from opposing ends of the chamber, receives heat through a first location of the chamber; generates in proximity of the first location a first pressure change associated with the transfer of a first portion of the received heat by the standing acoustic wave in the chamber; vibrates a first vibration member disposed within the chamber in response to the first pressure change; and generates a first voltage in response to the vibration of the first vibration member.
In another embodiment, the method also generates in proximity of the second location a second pressure change associated with the transfer of a second portion of the received heat by the standing acoustic wave in the chamber; vibrates a second vibration member disposed within the chamber in response to the second pressure change; generates a second voltage in response to the vibration of the second vibration member; and dissipates a third portion of the heat transferred via the standing acoustic wave at a second location within the chamber.
Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.